Metal degreasing agents

ABSTRACT

METAL DEGREASING AGENTS COMPRISING TRICHLORETHYLENE OR PERCHLORETHYLENE CONTAINING 1,3,5-CYCLOHEPTATRIENE AS A STABILIZER WHICH IS EFFECTIVE IN THE LIQUID AS WELL AS THE VAPOR PHASE. IN ADDITION, THE DEGREASING AGENT MAY ALSO CONTAIN A TERTIARY AMINE IN WHICH AT LEAST ONE OF THE THREE ALIPHATIC GROUPS IS UNSATURATED.

United States atent ice 3,642,645 METAL DEGREASING AGENTS Ludwig Schmidhammer, Burghausen, Upper Bavaria,

Germany, assignor to Wacker-Chemie G.m.b.H.,

Munich, Bavaria, Germany No Drawing. Filed Feb. 3, 1970, Ser. No. 8,402 Claims priority, application Germany, Feb. 11, 1969,

P 19 06 758.4 Int. Cl. C09d 9/00; Clld 7/22 US. Cl. 252-162 4 Claims ABSTRACT OF THE DISCLOSURE Metal degreasing agents comprising trichlorethylene or perchlorethylene containing 1,3,5-cycloheptatriene as a stabilizer which is effective in the liquid as well as the vapor phase. In addition, the degreasing agent may also contain a tertiary amine in which at least one of the three aliphatic groups is unsaturated.

Trichlorethylene and perchlorethylene are used in many technical process, primarily as solvents for fats and other organic substances, e.g. for extracting oils and fats, for dry cleaning and particularly for degreasing metals.

These chlorinated hydrocarbons have a tendency to decompose under the influence of heat, oxygen, light and water, forming acid products like hydrochloric acid or tarry substances. This causes considerable difficulties in the storage, shipment, use and reclamation of these solvents.

The above drawbacks arise especially during the degreasing of metals. The substances with a corrosive effect, affect the metal surfaces at the elevated temperatures which are customarily used. Thus metal salts are formed which catalyst the decomposition into hydrochloric acid and condensation to tar-like products. This results in losses of solvent, and work pieces with affected surfaces and soiled with tar-like products. The instability of non-stabilized chlorinated hydrocarbons is particularly evident on aluminum parts, but also on iron parts as well.

In order to avoid the disadvantages described above, particularly during the degreasing of metals, numerous stabilizers have already been suggested, many of which consists of compounds containing oxygen functions. Thus, Pat. No. 2,371,644 refers to alcohols, Pat. No. 2,371,645 mentions ether, Pat. No. 2,371,646 mentions oximes and British Pat. No. 884,823 mentions ketones. However, none of these substances shows real effectiveness. Also known are mixtures with a synergistic effect like alcohols with epoxides (Pat. No. 3,188,355) or low-molecular esters with epoxides (DAS No. 1,096,711). However, here concentrations of additives of up to 1 weight percent are necessary. Moreover, the epoxides have a toxic effect.

Also described as effective are amines alone or in admixture with other substances which are stabilizers. Thus Pat. No. 2,997,507 reveals the use of teritary amines where at least one of the three aliphatic residues is unsaturated, e.g. l-dimethylaminopropine-2. The application of such additives is limited, because the required large quantities of the alkaline-reacting amine attack amphoteric metals like aluminum. Moreover, their effectiveness is largely limited to the photo-catalytic and oxidative decompositions, while toward metals and metal salts they do not show any improved stabilizing effect.

I have now discovered degreasing agents for metals, consisting of trichlorethylene or perchlorethylene, which decreasing agents contain 1,3,5-cycloheptatriene.

The advantage of my degreasing agents is that they are stable against oxidative and light-induced decompositions as well as against metal and metal salt catalyzed decompo- 3,642,645 Patented Feb. 15, 1972 sitions. It is surprising that 1,3,5-cycloheptatriene, which contains three unsaturated double bonds, has the stabilizing effect mentioned, because so far only oxygen-containing compounds have been used as metal deactivators, and the unsaturated hydrocarbons were acknowledged to have only the effect of light and oxidation stabilizers.

Moreover, I have found that 1,3,5-cycloheptatriene, together with trichlorethylene and perchlorethylene goes over into the vapor phase. Thus the degreasing agents are stable even in a gaseous state. 1,3,5-cycloheptatriene shows good effectiveness in quantities of 0.01 to 0.5 weight percent, referred to trichlorethylene or perchlorethylene. Preferred are quantities between 0.0 5 and 0.2 weight percent.

The stabilizing effect of 1,3,5-cycloheptatriene can be enhanced by the addition of tertiary amines in which at least one of the three aliphatic residues is unsaturated. Preferred here is l-dimethylaminopropine-Z, particularly in quantities of 0.025 to 0.1 weight percent, referred to trichlorethylene or perchlorethylene. However, allyl diisopropylamine, triallyl-amine and propargyl diisopropylamine also show a good effect with 1,3,5-cycloheptatriene. Such mixtures generally contain about twice the weight amount of 1,3,5-cycloheptatriene in respect to tertiary amine. Particularly suitable was found to be a degreasing agent which contains 0.1 weight percent 1,3,5-cycloheptatriene and 0.5 weight percent 1-dimethylaminopropine-2.

The degreasing agents of the invention are of special significance for the degreasing of iron and aluminum, because even when subjected to long periods of the corrosive influence of iron chloride or aluminum chloride no decomposition is noticeable.

EXAMPLE 1 In a series of tests, samples of trichlorethylene or perchlorethylene are boiled under reflux in the presence of 0.3- g. water-free aluminum chloride and 1.0 aluminum shavings. Due to the presence of aluminum and aluminum chloride, the conditions correspond to the technical degreasing of aluminum. The decomposition speed of trichlorethylene or perchlorethylene serves as the measure of the stabilizing effect of the additives. Consequently the period until the occurrence of tar-like products is measured. In the following tests 1 to 5 the stabilizing effect on trichlorethylene was tested, and in test 6 that on perchlorethylene.

above-described combination of the invention.

EXAMPLE 2 A second method for testing the stability of trichloroethylene toward aluminum consists of determining the weight loss of aluminum strips which were exposed to trichloroethylene under the influence of light and heat, and the acid content during the reflux treatment. Accordingly, one aluminum platelet of known weight is hung in the flask, one in the cooler and one in the extractor of a Franz Soxhlet apparatus, and ml. trichloroethylene which was mixed with 0.2 ml. water, are exposed for 3 days to the light of a dull-surface IOU-watt incandescent bulb which shines from a distance of 3 cm. on the side arm of the Soxhlet extractor. By means of a SOO-Watt hot plate so much heat is provided that the siphoning cycle repeats itself every 8 to 10 minutes. The exhaust gas escaping over the cooler is piped into a rinsing flask filled with distilled water in order to catch any acid that might have formed.

After refluxing treatment for 72 hours the acid content is determined by titration of an aqueous extract together with the exhaust gas rinse Water with 0.01 N soda lye against phenolphthalein as the indicator. In case of an effective stabilization no acid titer should appear after the test period. The weight losses of the aluminum platelets are determined by differential weighing.

The invention claimed is:

TABLE 2 Acidity, Weight losses in mg.

Test Number Additive HOl Retort Cooler Extractor None O. 03 185 163 198 0.1% 1,3,5-cyc1oheptatriene 0 0.3 0. 1 0. 4

0.05% 1-dimethylaminopropine-2 0. 001 0. 7 0. 3 0. 8

0.1% 1,3,5-cycloheptatriene plus 0.05% l-dimethylaminopropine 0 0 0 0 The lower weight losses of all aluminum platelets indicate that the stabilizer is also effective in the gas phase.

EXAMPLE 3 TABLE 3 Test Acidity, T duration percent No Additive (hours) HCl 1 None 11 0. 03 2 0.1% 1,3,5-eycloheptatriene 142 0.02 3 0.05% l-dlmethylamlnopropine-2 189 0. 06 4. 0.1% 1,3,5-eycloheptatriene plus 0.05% 798 0. 03

1-dirnethylaminopropine-2.

ylene, and a content of 0.025 to 0.1 weight percent of 1- dimethylaminopropine-2, referred to the trichlorethylene or perchlorethylene.

References Cited UNITED STATES PATENTS 3,291,745 12/1966 Martens 252364 2,997,507 8/1961 Monroe et al 260652.5 2,831,906 4/1958 \Vinberg 260-666 A LEON D. ROSDOL, Primary Examiner W. E. SCHULZ, Assistant Examiner US. Cl. X.R. 

